Google search , span of school grades...***Grade span**** means (1) from birth to preschool; (2) Kindergarten and grades 1 to 6, inclusive, including transitional kindergarten; and (3) grades 7 to 12 inclusive. Grade span: the categories into which a district groups its grades of students; i.e., elementary, middle or junior high school, and high school.
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https://www.linguee.com/english-chinese/translation/numerica...

examples of span, range, range of classes...English This table displays by grade level the average class size and the number of classrooms that fall into each size category (a range of total students per classroom). Parallel text 本表依年級顯示平均班級大小，以及不同大小 (每間教室的總學生人數) 的教室數目。 https://www.linguee.com/english-chinese/search?source=auto&q...

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Note added at 1 hr (2021-12-16 03:52:02 GMT)
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Grade apan, grade is an adjective,

the school grade, the level or year of the student SECOND word Span is a noun, meaning the range of the school years form first graders for example, to 4th graders, the span is from first graders to fourth graders, that is a range of levels, or A SPan of levels.

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Note added at 1 hr (2021-12-16 03:56:50 GMT)
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It is often confusing becaus there are many meanings of SPAN, and many Of Grade.

Grade......the year or level of the student, first grade, 5th grade,

Grade,...(what is not the meaning in your question ) .the note or evaluation of how well the student studies, in grading A is the best, Fi is Failing,

Grading in England, really good evaluation is OH, letter O,,

In Costa jRica, really good grade is 10, that is TEN.

grade span 是指连续的几个年级，比如K to 3rd grade，8 to 11 grade，etc.

a grade, grade span, school, or district to all eligible students.

一个年级、数个年级、整个学校或整个学区。

across 这里的意思是“遍布”，可以转为“在......之中”

加上 across 的整个短语的译文: 在一个年级、数个年级、整个学校或整个学区之中

Grade span means the range of grades within the same school.

对某个年级、某些年级、学校或地区所有符合条件的学生进行统一管理。

Grade: 年级
例如：Grade 1 to 12 (1 至 12 年级).

Grade span: 年级组别 / 年级跨距
例如：Elementary school grade span is from grade 1 to grade 5.
Middle school grade span is from grade 6 to grade 8.
High school grade span is from grade 9 to grade 12.

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Note added at 9 hrs (2021-12-16 12:41:45 GMT)
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小學的年级组别是由一年級至五年級。
初中的年级组别是由六年級至八年級。
高中的年级组别是由九年級至十二年級。

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Note added at 10 hrs (2021-12-16 12:59:27 GMT)
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uniformly 和 across 是 administered 動詞的兩個副詞。
uniformly administered across 的意思是 “從頭到尾劃一地實行”。

Uniformly administered across a grade, grade span, school, or district to all eligible students.
對所有每個年級，年級組別，學校或學區符合條件的學生從頭到尾劃一地實行。

Grade span, or grade configuration, is the range of grades that a school comprises. In Bangor, where the first author’s children attended school, students begin their education career at
a k-3 school, proceed to a 4-5 school, then a 6-8 school, and finally to the 9-12 high school.